docs: def set_default_backend(name: str):
      """Choose a default backend."""
      global _default_backend
      if name == "bokeh":
          raise RuntimeError("Support for bokeh has been discontinued. At some point, we may return to support holoviews.")
      if not name in backends:
          raise RuntimeError("Backend {0} is not supported and cannot be set as default.".format(name))
      _default_backend = name